


Sample Size: One

by TroubleIWant



Category: Teen Wolf (TV)
Genre: Alternate Universe - Canon Divergence, Anal Sex, Bottom Derek, Cowgirl Position, F/M, Fingering, First Kisses, Getting Together, M/M, PWP, Rule 63, Shenanigans, Temporarily female-bodied Stiles, and various other firsts, just general smuttiness, that's not how a scientific study works Stiles
Language: English
Status: Completed
Published: 2017-01-18
Updated: 2017-01-18
Packaged: 2018-09-18 07:55:33
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 5,920
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9375434
Author URL: https://archiveofourown.org/users/TroubleIWant/pseuds/TroubleIWant
Summary: This is what it says on the tin: Stiles gets a girl body and then he and Derek bang. Also there are feelings, because this is me.-OR-“Scott,” Stiles says slowly, “I may literally be the only person ever who gets to compare the male and female orgasm from a first person perspective. In the history of the world! Anyone who bones me in the next 24 hours is contributing to the sum of human knowledge. It would be irresponsible not to!”“Well, it’s your body,” Scott shrugs. “Be safe, I guess?”





	

**Author's Note:**

> Firstly, big thanks to [Matildajones](http://matildajones.tumblr.com/) for her mad beta skills!
> 
> Secondly: Regarding the Rule 63 set up - this fic skirts around gender identity issues in much the same way that most sex-pollen/ABO in heat/fuck or die fics skirt around consent issues... which is to say, it sets them aside. While I hope I haven't written anything offensive (and am happy to be corrected if I have!) and do use male pronouns throughout as Stiles still thinks of himself as male, the focus here is on fun sexy times, and wedging in a scene where Stiles breaks down all his feelings about having a female body didn't feel right. Here in the notes, however, I'd like to point out that the Stiles in this fic is at least a little gender-fluid, and that his nonchalant reaction to events wouldn't be everyone's reaction - or even the most common!
> 
> In any case, if you're cool with the above caveats, I hope that you enjoy the absolute smuttiest thing I think I've ever written good lord.

“Someone needs to sex me right now!” Stiles demands. It comes out a bit higher-pitched than usual, which makes a certain amount of sense considering that his latest spell-gone-awry has temporarily given him a female body.

“Yelling that in my living room isn’t the most foolproof way to get laid,” Scott points out incredulously, “And, like, is that really your biggest concern right now? I’d be super weirded out if I was suddenly a girl.” 

Stiles rolls his eyes; he’s not a girl, he’s just got a female body for a while. Which is honestly kind of cool if you ask him.

Scott just makes a face. “Maybe you should just sit tight until this wears off, like Deaton said?”

Again, Stiles has to roll his eyes. Scott is a great friend and a pretty okay werewolf, but he does lack a sense of adventure at times. “Scott,” Stiles says slowly, “I may literally be the only person  _ ever _ who gets to compare the male and female orgasm from a first person perspective. In the history of the world! Anyone who bones me in the next 24 hours is contributing to the sum of human knowledge. It would be irresponsible  _ not _ to!”

“Well, it’s your body,” Scott shrugs. “Be safe, I guess?”

“So, does that mean you’ll, you know,” Stiles waggles his eyebrows, “help a bro out? For science?”

“No,” Scott says, more quickly and firmly than is really called for.

Malia also says no ( _ I broke up with you, Stiles _ ), as does Lydia ( _ This is not how science experiments work _ ), Parrish ( _ What? Oh my God, I work with your father! _ ) Kira ( _ uh, I mean, I like you? But not like-like you? Like that? _ ) Liam ( _ I wish I could help, but you’re still actually a guy and I’m not homophobic or anything but...maybe ask Mason? _ ), Mason ( _ Sorry, man, the boobs aren’t really doing it for me _ ), Cora ( _ no explanation - she just starts laughing, loudly _ ) and even Isaac “experimentation is my middle name” Lahey turns him down ( _ I’m in  _ France _ , and how did you get this number? _ ). 

Which is how Stiles finds himself at Derek’s loft. He kind of wishes he’d put on lipstick or mascara or something. Would he look good in lipstick? Maybe not. He isn’t a particularly pretty woman, as it turns out - he’s still slim and a bit gawky, his hair didn’t get any longer just because he got a vagina, and he’s wearing the same clothes he put on as a boy this morning. His boobs are nice though. Maybe a bit on the small side, but perky. You don’t need more than a handful, anyways, right? Well, they’re not quite a handful for him, but he has pretty long fingers, so.

Derek opens the door wearing a soft, worn pair of sweats and that goddamn white tank top that has a recurring role in Stiles’ wet dreams. Stiles waves cheerily and casts a significant glance down at his own transformed body. Derek’s eyebrows make a run for his hairline.

“...What did you do?” Derek asks after a long pause.

“So, funny story. Deaton thought maybe I could get better at using my spark thing? But I was practicing on this rose bush and I was thinking flowery, feminine thoughts and then. Well. Ta-dah!”

Derek’s eyebrows edge impossibly further up his face. “Is it permanent?”

“Noo-ope,” Stiles says, rocking back on his heels. “Thankfully. Deaton says it’s pretty impressive that I did this to myself at all and it should reverse itself in 12 hours. More like nine at this point.”

“Right,” Derek says as Stiles ducks under his arm, into the loft. “So what are you doing here?” 

“Well, so I was thinking,” Stiles starts. He can feel his face burning he’s blushing so hard. “It’s not every day a teenage boy gets to, ahem, experience  _ certain things _ from the, er, other side. If you know what I’m saying. Purely for the sake of understanding, well,  _ physiological _ differences to very specific stimuli, I thought that perhaps it would be educational to experiment with, or, well, to have someone help me experiment with...you know...”

“You want to have sex,” Derek deadpans.

Stiles is so, so glad he doesn’t have to keep talking. “Yes, exactly, thank you! I’ve already asked everyone else,” he adds quickly. So Derek doesn’t think Stiles is singling him out, or anything weird.

“Everyone?” Derek echos, unimpressed. “Your idea of a come-on is telling me I’m literally the last person on your list.”

Stiles fakes a big grin, stuffing his hands in his pockets and giving an exaggerated shrug. Considering this is probably the best opportunity he’s ever going to have to get into Derek’s pants - which he has wanted to do since approximately forever - he’s not sure himself why Derek hadn’t topped the list. Except that this gambit either ends in him being turned down cold or in him actually getting what he wants… and then never getting it again, because Derek’s only into female bodies and Stiles won’t have one tomorrow. 

Puts a bit of a damper on things, you know?

At the moment it looks like option one, for better or for worse. Derek’s face is scrunching up in a weird, annoyed expression that probably means he’s thinking of exactly how to say “no” in a way that’s mean but not cruel. For all the growling, Derek’s never cruel. 

So, fine. Not surprising. Stiles can’t help but remember that Derek’s previous flings are all curvy and gorgeous in a way that he is distinctly not. Ladies who are hot like Derek is hot:  _ incandescently _ . Where as Stiles is more… at-the-right-angle-with-a-good-filter hot.

But Stiles still  _ wants _ , so badly. The thin material of the tank-top hugs Derek’s pecs when he crosses his arms, and the soft sleep pants are riding pretty damn low on his hips. While Derek is deliberating, Stiles leans back against the wall and for once just lets himself  _ look _ , reveling in the impossibility of an awkward boner. He lets himself imagine what it would feel like to run his hands over Derek’s back, to have Derek’s mouth on him, stubble scraping rough against his neck in counterpoint to his soft, wet lips... 

“You really want to do this?” Derek interrupts, replacing fantasy with reality. 

“What?” Stile says, head spinning as his mind tries to catch up with the crazy fact that Derek is actually  _ not _ turning him down cold. And then Derek is suddenly all up in his space, one hand braced on the wall just beside Stiles’ head and leaning in really, really close. Stiles could probably count his eyelashes. 

“Do you want me to fuck you,” Derek asks again, softly but with crisp enunciation that gives the question a heated edge.

“Oh! Uh, yeah,” Stiles breathes, heart pumping fast enough to back up exactly how much he means it. “Definitely.” 

“Good,” Derek murmurs, tilting his head to a perfect kissing angle and drawing even closer - but not close enough to touch their mouths together, not yet. He pauses a breath away to just smoulder instead, dropping his eyes to Stiles’ mouth before looking back up into his eyes. It’s pretty intense, which is to say intimidating, but Stiles realizes that instead of pressing his head back into the wall like Derek’s got cooties, he should maybe initiate.  _ So _ , he thinks as he moves to press his lips against Derek’s,  _ here goes nothing. _

Derek is a pretty good kisser, as it turns out. He’s gentle but not boring, using his lips and tongue to work Stiles’ mouth open, nipping lightly at his bottom lip. He brings one hand up to curl around Stiles’ face and turn his head just so, thumb stroking his cheek. The kiss is so slow and easy that Stiles doesn’t quite realize that they’ve gone from mostly-closed mouthed smooching to frenching so deeply he’d probably have to unhinge his jaw to get up any farther in Derek’s business.

Stiles’ arms have somehow ended up thrown over Derek’s shoulders, too, and their bodies are pressed tight together against the wall. It feels - well, Stiles can hear little needy whimpers coming out of him that he had no conscious intention of making. Derek makes this tiny moaning sound like he’s tasting something delicious, but then he pulls back. Stiles’s face tips after him, chasing the kiss.

“So?” Derek asks quietly.

“Lady body winning so far,” Stiles gasps.

Derek grins, cocky and a little smug. Oh God, rewind, thinking about Derek actually wanting to impress him too hot to contemplate. While Stiles squeezes his eyes shut and tries to calm down, Derek reaches down to grab Stiles’ thighs and pulls him up. On instinct, Stiles goes with it, wrapping his legs around Derek’s waist. His crotch is pressed tight against Derek’s abs, and the seam of his jeans is a delicious ridge against his clit. He grinds down into the sensation, equally turned on by the friction and by how effortlessly Derek is carrying him over to the bed.

He kind of expects to get tossed onto the sheets and pounced on, but Derek doesn’t do that. He puts a careful hand at the small of Stiles’ back to keep their bodies close as he kneels on to the edge of the bed and shuffles forward before he lowers them down as one in the center of the mattress. It’s unexpectedly sweet, but also incredibly hot - maybe hotter than getting tossed around. Not that Stiles can make an informed list of pros and cons. He’s struck by the unpleasant thought that he’s not going to get a second opportunity for comparison.

The thought gives him a desperate edge, and he pulls Derek down for another, rougher kiss. Derek doesn’t break it, not even when he arches his back to lift his chest off Stiles’ and begins to unbutton Stiles’ plaid overshirt. He shoves it off Stiles’ shoulders, then sits up to strip out of his own shirt in one fluid motion, dragging it over his head by the collar. Stiles yanks his arms free of the plaid shirt and sends it flying after Derek’s tank. He obviously hadn’t been wearing a bra, so his nipples poke up from his thin undershirt. Derek trails a finger over one, rubs back and forth, pinches lightly, cups the whole breast and squeezes.

“ _ Oh _ , keep doing that,” Stiles sighs. 

“No,” Derek says playfully. Stiles huffs in annoyance, but before he can do more Derek pushes his undershirt up over his breasts and runs his fingers over the suddenly exposed skin.

“Oooh, no, keep doing  _ that _ ,” Stiles moans when Derek takes one of his nipples in his mouth, kneading the other one with firm, gentle pressure.

“Take your pants off,” Derek instructs, and Stiles hurriedly complies, or tries to despite clumsily fumbling with his fly because Derek’s mouth is fucking  _ distracting _ and he’s having a practically religious epiphany about why having breasts is amazing.

Derek moves down the bed to help him pull the pants all the way off, and then he’s kneeling between Stiles’ knees, and Stiles realizes that they’re going to be naked soon. Like,  _ naked _ naked.

And if he wasn’t feeling ridiculous enough with his spindly legs sticking out from his men’s medium plaid boxers… girls only have beautiful hairless legs because they shave, obviously, but somehow he’s still surprised to see his own covered in a light dusting of brown hair. All of a sudden he feels exposed, very aware that there’s no way to hide, well,  _ anything _ from Derek like this. 

“Ugh, sorry,” he says, giving the hair a pointed look.

“What… this? You really think having body hair makes you unattractive?” Derek asks with his signature eyebrow quirk, running his hands up Stiles’ fuzzy shins.

“Well, sure,” Stiles says, blushing. “That and like, my  _ face.”  _  And the boyish hips, and his weird bony hands, and the moles, and…

Derek blinks at him like he’s grown another head. “You’re beautiful,” he corrects, sliding his hands back down Stiles’ legs like they’re valuable, perfect. And Stiles? Well, he could fucking get used to this treatment.

Derek takes an ankle pulls it up behind his own hip, spreading Stiles’ legs. Stiles pulls back a bit, stiff with nerves. “Aren’t you going to get naked, too?” he blurts.

Only then does Derek seem to realize he’s not, going so far as to glance down at his sweats in surprise. He makes quick work of the clothes, peeling the pants and boxers off as one. Or maybe he was just going commando. Stiles almost swallows his tongue.

Derek seems so unaffected by his own nudity that Stiles feels almost calm as Derek helps him take his own boxers off. He presses his legs tightly together as soon as he’s able, though, glad that all his bits are, at least for the moment, neatly tucked away from view or comparison. Naked in bed with Derek… he’s imagined this so many times, but in all his fantasies, he’d skipped over how vulnerable this part feels.

Derek nuzzles his jaw, a weirdly feline gesture considering his genetic wolfitude, but Stiles takes the hint and turns into him so that they can kiss again. It’s tender and gentle, and it’s pretty funny how kissing Derek is already a comfortable home base for Stiles. He loses track of his anxiety, and it’s only when he notices how he  _ isn’t _ noticing any racing heartbeat that he figures it out. Kissing is Derek’s way to get him comfortable again. 

Weirdly, the thought doesn’t embarrass him. In fact, knowing that Derek of all people is going to be so gentle with his anxiety pretty much kills any remaining hesitation. Stiles kisses back with enthusiasm, eager to let Derek know that he’s... Stiles doesn’t know,  _ doing this well _ . Making Stiles feel wanted and special, even though he’s really not.

As their kisses go hot and sloppy, Derek’s hands wander. To Stiles’ firm breasts and peaked nipples again, then down to the gentle swell of his newly feminine hips, dragging inwards towards the crease at his thigh.

“This okay?” Derek asks softly, looking up at Stiles with an expression that’s questioning and almost shy.

“Yeah,” Stiles confirms, equally softly.

Derek’s hand moves further inwards, dipping into the wetness between Stiles’ legs. His fingers rub experimentally around Stiles’ clit, circling and then pushing into him slowly. It’s weird being penetrated so easily; Stiles is used to all the tricky prep of anal, with lube and stretching and the weird angle of his own wrist. This way is so easy in comparison; there’s less friction, but he recognizes the sensation of being filled. He isn’t sure how much of the difference is the new body, and how much is the fact of Derek. The man’s clearly experienced, continuing to finger him expertly while he leans back in to resume their kiss. It’s so much sensation that Stiles can’t even keep track of exactly what he’s doing. It all blurs together into one amazing feeling, a building warmth buzzing low in his stomach. His legs are starting to tremble, his toes curling, and he identifies what’s happening just in time to stop it.

“Ah, no,” he says, grabbing ineffectually at Derek’s hand. And then the hand is gone,  _ everything’s _ gone, Derek’s not touching him at all, anywhere.

“What? What happened?” Stiles asks, dazed.

“You asked me to stop.” Derek sounds harsh, as if he’s irritated, but Stiles knows him well enough to tell that what the tone really means is that he’s scared. Like doing something wrong or stopping this is the last thing he wants, even though it’s just a stupid favor for the stupid kid he... well, does technically owe his life to.

“It’s good just, too much,” Stiles assures him. “I was uh, close. And I don’t want to come yet.” 

Derek’s concern instantly transforms to relief, and then bemusement. “Why not? You do know that part of the package is you get to come at least twice, or I’m not doing my job.”

“...Oh, fuck me,” Stiles says, a liquid want pulsing into his groin and making him squirm.  _ Multiple orgasms _ , how the hell did he forget multiple orgasms?

“In a minute,” Derek grins. 

He moves his fingers back to what they were doing, only now he’s kneeling down there, too, instead of holding Stiles. In fact, his whole face is sort of right there up in Stiles’ business, and before Stiles has a chance to get self conscious about it, there’s the hot wetness of Derek’s tongue lathing Stiles’ cunt, there’s his lips sucking at his clit, there’s the barest roughness of beard on his thighs. Stiles thinks he may literally see stars as the longest orgasm of his life takes him by surprise, the rolling waves of shivery muscle contractions bleeding into a fuzzy blur of warm pleasure through his entire body.

When he finally comes back to himself, Derek is looking down at him like he’s drinking the sight in, his expression hungry and - oh yeah - his cock hard and red, dripping precome already though Stiles hasn’t even touched him. He has the sudden realization that he’s being kind of selfish. He should at least offer a a hand job or oral… though that would decimate the pretence of this visit being just some goofy experiment, he supposes. What he should really do is fuck Derek. That was the plan, after all. Only problem there is that the idea of P-in-V sex is daunting, if he’s honest. Despite his bravado with Scott, he’s a little unnerved to even have a “V,” much less consider using it for anything.

Buying time, Stiles rolls out from under Derek and leans over the edge of the bed to fish for his pants. He grabs a condom from the back pocket when he finally gets at them, and sits up triumphantly. He holds the shiny foil up between two fingers like a playing card, waving it at Derek. “Brought this. I mean, kind of guessing you already have some around but. Uh. Here.”

Derek leans back, flicks his eyes down at himself. “You wanna?”

“Eh, sure,” Stiles says mockingly copying Derek’s nonchalance. Internally, his brain is a cavalcade of  _ hot damn _ ,  _ yes please _ , and  _ unff _ . Of course he wants to get his hands on that, like,  _ yesterday _ . 

He opens the packet with trembly hands, makes sure it’s the right way around pinches the tip before he rolls it down. He strokes down the sides of Derek’s cock, unconsciously measuring the girth, appreciating the way Derek’s warm skin moves over his hardness. Hand jobs he understands, considering he’s typically in possession of a penis himself. Anyways, it’s a pleasant distraction for the uncertainty of what comes next.

“You’re nervous,” Derek says, and it’s not a question.

Stiles whuffs out a breath, half annoyed and half relieved to be called out. “Sure, yeah. I mean, obviously? You’re  _ you _ and I’m maybe not a virgin anymore, but I’m not all that experienced, either. Plus I don't usually have this particular equipment,” he finishes with an irritated gesture towards his body. 

“It’s not about experience,” Derek says.

“Yes, it is,” Stiles retorts hotly. “Sex is a skill like everything else, it’s a physical coordination thing and I’m not being humble or whatever when I say that I genuinely don’t have that. Or stamina, really, or flexibility, or...”

“Stiles,” Derek interrupts patiently. “You’ll be good, really. I promise you that I’m going to enjoy this.” He quirks his eyebrow and it’s crazy but it seems like he really cares. Stiles presses his lips together. He’s losing sight of what this is again. It’s just a dumb experiment brought on by some weird supernatural turn of events. It’s not dating. Hell, it’s not even being fuckbuddies.

“Here,” Derek says, rolling on his back, and beckoning. Stiles shuffles up on his knees, then gulps when Derek reaches down and encourages him to straddle him. His dick is really, really close to Stiles’ cunt. His hand is warm on Stiles’ thigh, rubbing. 

“We can do it however you want. Or if you want to go back to oral, I’m good with that. We don’t have to do anything you don’t want.” 

Stiles is half paying attention, but mostly he’s just looking down at Derek’s dick. It’s a bit obscured by the condom, yes, but now he knows the exact girth and heft of it, the slight curve, the shape of his balls. “No, I think we might have to actually,” Stiles says faintly.  It would be a serious waste to come so close and then not get on that, honestly. If nothing else, he’ll have some amazing material for jerking off during the inevitable lonely nights to come.

“Okay,” Derek says, his tone carefully nonchalant. But the breath he takes after shudders in his chest, and his cock twitches like he wants this as badly as Stiles does.

Stiles scoots up so the head of Derek’s cock rubs into the slick between his legs, catches gently at his entrance. He stays poised there for a second, hovering right on the edge of penetration with a delicious anticipation. He reaches down to get the angle right, guiding Derek with his hands, and then sits down into it. Like when Derek fingered him earlier, it’s unexpectedly slick and easy as Derek slips into him, But this time there’s a sharp pain of over-stretch, and Stiles wonders belatedly if he has -  _ had _ \- a hyman.

He swirls his hips experimentally, and Derek makes a  _ noise _ . Fuck, that’s gratifying. Any pain has quickly faded to soreness, and even that is being overwhelmed with arousal. Derek’s cock feels amazing inside him. Everything feels amazing, actually, from his cunt to his fingertips to the tips of his ears. His whole body feels plush and overheated, his skin is buzzing with sensation. He lets his palms roam over Derek’s body, and Derek clutches his waist tight, urging him to move.

So he does, and then he’s riding Derek Hale. He’s having sex with Derek Hale, he is currently bouncing on Derek Hale’s dick, which is inside him, because they’re having sex. He’d be freaking out about that if it wasn’t impossible to focus on anything but the way he feels right now. And how he feels is  _ almost impossibly good _ . 

It’s not in the same way as before, though, back when Derek first made him come. He isn’t getting quite enough of the right friction to orgasm again, though it’s enough sensation that he wants to - badly.  He tries leaning forward, arching back, searching for the feeling from earlier, that release when Derek pushed him over the edge. When he gets his legs spread open just a bit wider and leans forward, he finds he can rub his clit almost enough when he grinds down. So that’s what he does, eyes closed, mouth hanging open as he works to find his release. Sweat’s pricking on his forehead, but he’s too far gone to care about that, or the weird faces and noises he must be making.

The next time he grinds down, struggling for that hint of friction, he encounters something much better; the hot pad of Derek’s finger. He moans, a shiver running up from his knees to his spine.

“That good?” Derek’s voice is husky.

“Mm,” Stiles confirms, unable to put words together at this particular juncture.

“Let’s try...” Derek says breathlessly, and Stiles is suddenly being moved. First Derek pushes one of Stiles’ legs back over his own thighs, and then Stiles finds himself looking down at Derek’s feet in reverse cowgirl; the change in perspective is a little funny until Derek tugs him down snug to his chest. Stiles’ back is arched enough that he’s still taking most of Derek’s cock, his legs folded and spread. It’s enough of a stretch that he feels it in his thighs, but not uncomfortably. 

In this position Derek ends up doing more of the work, curling in with his abs to fuck up into Stiles. The thrusts are admittedly shallower than before, but the length of Derek’s cock sliding into Stiles at this angle is plenty satisfying. Even better, the new configuration gives his hand free range over Stiles’ clit. 

He rubs tight little circles, speeding up at Stiles’ choked instruction. Derek’s breath goes ragged at the reactions he’s drawing out, to the point where he’s panting harshly in Stiles’ his ear. His arms are trembling a little, the free hand clutching at Stiles’ breast, and Stiles can tell that he’s getting off on this, getting off on Stiles’ body... Stiles whimpers and twitches with arousal, muscles in his legs tensing as he tries to give as good as he’s getting. Derek moans, kissing his neck sloppily, squeezing his breasts. It’s a feedback loop of noise and arousal and reaction until Stiles’ second orgasm crests and washes over his entire body, harder and faster than his first. 

Derek holds him through it, tightly enough that it’s just barely on the right side of uncomfortable. Stiles is so sensitive he can feel the way Derek’s cock twitches as he comes a moment later, with his nose buried in the crook of Stiles’ neck.

Stiles goes slack with post-coital bliss, wrung out and shivery. Derek eases out of him, kissing his neck sloppy and gentle as Stiles kicks his legs out straight and stretches out the toe-curling tension.

“You’re really, really good at this,” Stiles murmurs.

“We’re good at this,” Derek corrects, trailing his fingers lightly through Stiles’ hair. It's perfect - except for how it’s temporary. That part is pretty damn terrible.

“I should go,” Stiles says, rolling off of Derek. He makes no further effort to get out of bed, though. As much as he wants to belatedly protect his heart, he doesn’t quite have the heart to put an end to this.  The petting and cuddling is making Stiles feel like this is something more than the one-off adventure he knows it is, but that said… the illusion is pretty damn pleasant. Also, he’s exhausted.

“You can stay.” Derek's fingers have stilled, and he curls into Stiles, spooning all up against him. It’s nice, being held against all that warm skin, even if it is a bit sticky. 

“Okay,” Stiles says, and before he has much more chance to over-think things, he’s asleep. 

 

* * *

 

 

He wakes up in his regular male body, as if everything about the last day had been some weird fever dream. Except that he’s in Derek’s bed, still in Derek’s arms, and his thighs are deliciously sore. For a second it’s nice, right up until he remembers: here’s the part where Derek is grossed out by his flat chest and his dick, where things go back to the normal bitching and the bantering and the wanting and the never, ever touching. Here’s the part where he goes back to his real life, except now he’ll be stuck with his impossible crush  _ plus _ intimate knowledge of exactly how tenderly Derek kisses women.

Derek stirs awake, maybe at Stiles’ thunderous heartbeat, and Stiles shies away from him. While he’s still stretching and blinking into full alertness, Stiles makes sure that the sheets are covering up all his bits, throat to toes. 

Even once he’s fully awake, Derek isn’t taking the same care; his lazy stretch shifts the sheets enough to expose his hipbone and a trail of dark hair and Stiles is human, okay? Of course he's staring.

He knows the deal is over now, though, and he drags his eyes guiltily up to Derek’s. Only Derek doesn’t look grossed out at Stiles’ transformation back into himself. His eyes are heavy-lidded, dark, and the overall effect is that he looks… kind of turned on? 

Stiles accidentally lets the sheet he’d been clutching fall to his waist in surprise. Derek’s eyes dip down to the newly exposed skin, tracing over Stiles’ chest hair and the dark hickeys he left on his neck and collarbones the night before. He looks even more turned on, a possessive smile transforming his expression into something hungry. So maybe, Stiles thinks with a jolt, Derek is not exclusively about female bodies, in the same way he wasn't exclusively about the curvy gorgeousness. 

And because Stiles believes in nothing so much as pushing his luck, he says, “You know, for a true comparison, we should actually do a control group, so...”

That’s all the encouragement Derek needs to tackle him back onto the bed and kiss him silly, which is how Stiles learns that the tenderness of the previous night is not how Derek kisses women, it’s how he kisses  _ Stiles _ , no matter what he happens to look like.

It’s kind of overwhelming. 

“I should blow you,” Derek says when he comes up for air, “for comparison’s sake.” The way he makes the offer is casually conversational, but also a bit knowing, as if he realizes full well the whole comparing orgasms thing was just a flimsy excuse for Stiles to get them here. Yet somehow he’s not pissed about that? Stiles finds himself hesitantly hopeful.

“Uh, yeah,” Stiles agrees, breathlessly. “So I guess you swing both ways, then? You’re bi?”

“I prefer pan,” Derek corrects, winking. Then he dips down a bit more and his mouth is on Stiles’ cock and well.  _ Well _ . 

He’s just as skilled with the blowjob as he was with eating Stiles’ temporary cunt. He takes Stiles’ cock all the way into his throat, swallowing tight and hot around it, swiping his tongue across the bottom as he pulls back… Stiles tugs him off, embarrassingly shortly after he starts, to keep blowing his load right then and there. Strike one for having a penis; this time there’s not going to be a second shot if Stiles comes.

“Okay, I’m gonna need a bit more prep before we fuck this time,” Stiles says breathlessly. He hadn’t thought he’d get two cracks at Derek’s cock, but now he doesn’t want to waste any time. “Where’s your lube?”

Derek does not share his urgency. “You need prep?”

“Um, yes,” Stiles says, a little shortly. “It’s not a self lubricating asshole. I don’t know about freaking werewolf physiology, but...”

“No, no, I know. Werewolves need lube before anal too.” He’s looking at Stiles leadingly, almost...hopefully?”

“Uh,” Stiles says, too much of his blood in his dick to really put two and two together.

“For a fair comparison,” Derek says slowly, “you should take advantage of all the equipment, right? Girls can get anal. Can’t really give it, though.”

“Well, you know, with the right toys a girl could definitely… you know, there’s actually a term for that, it’s called pegging, Dan Savage...” Derek raises an eyebrow. “By which I mean, yeah, I see your point.” Stiles swallows hard to keep from blabbering on any more. Is Derek really suggesting what Stiles thinks he is?

“So,” Derek says, slowly again. “You want to fuck me?”

“Yeah,” Stiles says, nodding. “Yeah, yes, definitely.” He’s clearly fallen into some alternate reality porno version of his life, and he hopes he never falls back.

Derek get the lube, dribbles it generously on his blunt fingers. He kicks the sheets away, spreads his legs and starts to work himself open, sure and practiced. Stiles kneels between his thighs, just… looking. God. 

“Little help?” Derek asks, almost sounding strangled his voice is so tight with arousal. Stiles puffs out a breath and then he does help, sliding in one finger in beside Derek’s two and using the other hand to grip himself hard at the base of his cock so he doesn’t nut right at that, the feeling of hot tight wet heat that, shortly, will be wrapped around him. He might actually die.

So instead of lining up and fucking Derek right away, Stiles leans down and kisses him, keeping his cock entirely out of the proceedings until he can calm down. Instead of fixating on what it’ll feel like to be inside Derek, he thinks about how thoughtful Derek’s been about this, about his dry sense humor, his bravery in the face of both tragedy and terror. Stiles kisses him tries to put all of the things he’s thinking into the press of their lips, the stroke of his tongue over Derek’s. He’s kneeling over him and bracketing his body around Derek’s as if Stiles can fend off the many bad parts of his past, the dangers still coming for them, as if they’re in love and this is more than just sex.

“Stiles,” Derek says, begs almost, and Stiles figures he’s as ready as he’s going to be. 

He reaches down to adjust himself, holding his cock steady as he pushes in. Even before he bottoms out - sometime around when the head of his cock pushes past the first tight ring of muscle, actually - Stiles is instantly back to being 99% of the way to coming. He holds off his orgasm through sheer will. Elbows braced on the bed, only letting himself acknowledge enough of Derek’s reactions to get the angle and pace right, he sets a steady rhythm. He wants this to be good, desperately. After all, if he impresses with this version of himself there might just be a second round on the table.

Derek writhes, moans, looks down at his painfully hard cock. “I need…”

“Yeah,” Stiles says, and stops moving so he can get a hand wrapped around him, figure out the best grip. He works his hand over Derek’s length, finding a pressure and speed that gets him squirming. His own cock is pressed inside deep, hips flush against Derek’s ass, filling him up. He doesn’t start thrusting again, but there are tiny movements as Derek squirms, gone on the sensation of Stiles jerking him and filling him up at the same time. It blows Stiles’ mind he’s the one is doing this, his body is making Derek’s body react like this. His breath hitches, cock pulsing where it’s still buried inside of Derek’s heat.

Derek comes hard, not a second too soon. Stiles rocks into him, unable to hold anything back any longer. He braces his hands for a better position, and gets himself off in a few hard, unsteady thrusts, pushing through the clenching and squeezing of Derek’s orgasm.

They both collapse, for the second time, in a sweaty, satisfied heap. 

“So?” Derek says leadingly, after they both get their breath back.

“Huh?”

“So which is better?” Derek asks, mostly as a joke but a hint of nerves pushing in at the edges. He really cares, Stiles realizes, what the answer is. He cares about Stiles having a good time, wanting more.

“This one,” Stiles says, soft and honest. He squirms into Derek’s sheets, shy about the admission even though he’s pretty sure at this point that his one sided pining has been less one sided than he assumed. “I like it this way.”

“Yeah?” Derek confirms, eyes searching Stiles’ face for truth or a cruel joke.

“Mhm,” Stiles assures him. “It felt real, doing it as myself.”

Derek’s eyes go soft, and he leans in and kisses Stiles in that same tender way as the first time. “I liked this way, too.”

“But just to be sure,” Stiles says, “we should probably try it again. You know, a few times at least.”

Derek nods, laughter sparking his eyes. “Absolutely. We should get a really good sample size before we draw any conclusions.”

**Author's Note:**

> Thanks very much for reading, kudos-ing (?) and commenting (!?) you lovely things, you! 
> 
> If you liked this, feel free follow me on Tumblr at [TroubleIWant](troubleiwant.tumblr.com) for lots of Sterek reblogs and other fics that will have absolutely nothing in common with this one because the only constant with me is that I write about Stiles and Derek. And that usually one of them cries.
> 
> (....Though honestly I could be convinced to write a sequel to this one featuring Derek being temporarily female-bodied and HATING IT, because it would be a cool way to dig into how varied people's conception of their gender and their bodies are, and how a situation like this could go a vastly different direction given a different set of the aforementioned conceptions... and also I could write different types of sex. So.)


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